Control apparatus for document stackers

ABSTRACT

A document level sensor for controlling movement of a platform as documents stack thereon. A document tail kicker carries a shutter plate for blocking light normally impinging upon a light sensitive detector. A document sensor is placed upstream of the stacker platform at a distance less than the minimum distance between documents. The outputs of the light sensitive detector and the document detector are connected to a logic circuit requiring simultaneous outputs from each so as to develop a signal for actuating a motor. The motor drives a lead screw for lowering the stacker platform. The logic circuit also detects a stacker full or stacker jam condition. The stacker full condition is detected by sensing the output of the light sensitive detector, the output of the document detector and a lower limit switch. The stacker jam condition is detected by sensing the occurrence of two successive signals directing the stacker platform to be lowered and an output from the light sensitive detector.

' [75] lnventors: David L. Johnston;

, [22] Filed:

United States Patent 1 1 Johnston et al.

11 3,722,879 1 51 Mar. 27, 1973 1 CONTROL APPARATUS FOR DOCUMENT STACKERS Marvin E. Nyberg, both of Rochester, Minn.

[73] Assignee: International Business Machines Corporation, Armonk, N.Y.

Mar. 6, 1972 211 Appl. No.: 231,936

[52] US. Cl ..271/47, 271/88 [51] Int. Cl. ..B65h 31/00, B65h 7/02 [58] Field of Search ..271/88, 86, 87, 45, 47

[56] References Cited UNITED STATES PATENTS 3,131,932 5/l96 4 Maidment ..271/87 3,630,517 1/1970 Erskat ..271/88 Primary Examiner-Richard E. Aegerter AttorneyDonald F. Voss et a1.

[57] ABSTRACT A document level sensor for controlling movement of a platform as documents stack thereon. A document tail kicker carries a shutter plate for blocking light normally impinging upon a light sensitive detector. A document sensor is placed upstream of the stacker platform at a distance less than the minimum distance between documents. The outputs of the light sensitive detector and the document detector are connected to a logic circuit requiring simultaneous outputs from each so as to develop a signal for actuating a motor.

The motor drives a lead screw for lowering the stacker platform. The logic circuit also detects a stacker full or stacker jam condition. The stacker full condition is detected by sensing the output of the light sensitive detector, the output of the document detector and a lower limit switch. The stacker jam condition is detected by sensing the occurrence of two successive signals directing the stacker platform to be lowered and an output from the light sensitive detector.

7 Claims, 9 Drawing Figures Patented March 27, 1973 3,722,879

9 Sheets-Sheet 1 Patented March 27, 1973 9 Sheets-Sheet 2 FIG. 2

Patented March 27, 1973 3,722,879

9 Sheets-Sheet 5 PEG. 3

Patented March 27, 1973 3,722,879

9 Sheets-Sheet 4 Patented March 27,1973 3,722,879

9 Sheets-Sheet 5 v 45 I0 46 a Patented March 27, 1973 3,722,879

9 Sheets-Sheet 8 FIG. 8

CONTROL APPARATUS FOR DOCUMENT STACKERS BACKGROUND OF THE INVENTION 1. Field of the Invention,

The invention relates to -control apparatus and more particularly to control apparatus for controlling the movement of a platform upon which articles are accumulating and still more particularly to control ap- 1 paratus for controlling the movement of a platform upon which articles are accumulating where an article deflector also is incorporated into the control apparatus.

2. Description of the Prior Art In order to properly stack documents upon a platform, it has been the practice to maintain the top document at a predetermined elevation with respect to the delivery position of the documents. In some instances, the stacker platform was lowered a predetermined amount for every document accumulating thereon as described in US. Pat. No. 2,910,294. Other prior art approaches include sensing the top document of the stack and maintaining the level of the top document within predetermined limits. When the-instant top document reached a predetermined upper level, the stacker platform was lowered a predetermined amount. Then as more documents accumulated, the upper level would be reached again and the platform would be lowered again. This process would repeat until the stacker was full. US. Pat. No. 3,107,912 is directed to apparatus representative of this latter type of control. I

Although the aforementioned approaches are generally satisfactory for certain types of documents and stacking speeds, they are relatively expensive and do not sense the stack height at the entry position of the stacker. For some applications it is critical to sense the stack height at the entry position in order to properly stack the documents, particularly since the stack tends to be higher at the entry position.

The present invention takes advantage of a document kicker which'is used to kick the trailing portion of a document being stacked out of the way of the leading edge of a document entering the stacker. The document kicker is located at the aforementioned critical position within the stacker and thus offers advantages over other top document sensors. A shutter plate is attached to the document kicker and cooperates with a light sensitive detector to generate a signal when it interrupts light normally impinging upon the light sensitive detector. However, since the document kickeris operated for every document entering the stacker, it is necessary to sense the signal from the light sensitive detector when the document tail kicker is in a static condition. The sampling of the light sensitive detector when the document tail kicker is in a static condition is accomplished by a document sensor located in the document path upstream of the stacker a distance less than the minimum distance between documents. This provides sufficient time for the tail kicker to be in sub stantially a static condition at the time the output of the light sensitive detector is sensed. If there is a signal from the light sensitive detector when the document kicker is in the static condition, then the top document has reached a predetermined upper level and the stacker platform is lowered a predetermined amount. Logic circuitry prevents lowering the document platform upon reaching a stacker full condition. Logic circuitry generates a signal indicating a stacker jam condition if there are two successive signals for lowering the stacker platform together with a signal from the light sensitive detector indicating that the document kicker is in the operated position.

SUMMARY OF THE INVENTION DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view showing the stacker platform in the elevated position and with no documents in the stacker;

FIG. 2 is a plan view of the apparatus illustrating the invention;

FIG. 3 is a rear elevational view showing the stacker platform elevating mechanism; FIG. 4 is an elevational view illustrating the condition where adocument has entered the stacker and the document tail kicker is potentiated by the document and with the next document to enter the stacker being upstream of the document sensor;

FIG. 5 is an elevational view showing the document of FIG. 4 settled on the stack of documents and with the document tail kicker resting upon the uppermost document and the next document to enter the stacker being in position to be sensed by the document sensor;-

FIG. 6 is a front elevational view illustrating the condition where the stack .of documents is holding the document tail kicker in position toactivate the light sensitive detector and the next document to enter the stacker is-in position to be sensed by the document sensor;

FIG. 7 is a front elevational view showing the stacker platform after it has been incremented downwardly so that the document tail kicker is not activating the light sensitive detector;

FIG. 8 is a front elevational view illustrating a document jam condition; and

FIG. 9 is a schematic circuit diagram of the logic circuitry for detecting conditions to move the stacker platform, for detecting a stacker full condition and for detecting a jam condition.

DESCRIPTION OF THE INVENTION With reference to the drawings and particularly to FIG. 1, the invention is illustrated by way of example as including upper and lower transport belts 10 and 15 respectively disposed to form a document conveyor for delivering documents to stacker 20. The documents 25 are captured between belts 10 and 15 so as to move with belts 10 and 15 which are driven in a conventional manner.

Document 25 leaves control of belts and at point 16 and travels in free flight until it impacts stacker backplate 21. As a document is being delivered to stacker 20, its leading edge engages an arcuate section '31 of document tail kicker 30. Document tail kicker 30 is essentially a cantilevered spring suitably mounted and functions to deflect the trailing edge of a document 25 downwardly toward stacker platform 22 so as to quickly move the trailing edge of document 25 out of the way of an incoming document.

Document tail kicker 30 carries shutter plate 32 for activating light sensitive detector 40. Shuttle plate 32 is very light in weight and substantially no additional force is imposed by plate 32 upon the document being stacked. Hence, this invention takes advantage of the fact that the tail kicker 30 engages (senses) the documents entering the stacker at a critical position without incurring any real disadvantages. Light sensitive detector 40 includes light source 41 and light sensitive element 42 as seen in FIG. 2.

I The document tail kicker 30 is operated every time that a document 25 enters stacker 20. Thus, the shutter plate 32 activates light sensitive detector 40 for every document entering stacker 20. Therefore, in order to sense the height of the stack of documents upon stacker platform 22, it is necessary to sample the position of the shutter plate 32 after an incoming document has settled down. This is accomplished by document sensor 45 which includes light source 46 and light sensitive element 47. Light source 46 is positioned to project light through an aperture 17 inbottom guide 18. The light from light source 46 normally impinges upon light sensitive light element 47. The minimum distance between documents is such that a document which has entered stacker will have settled down prior to a following document being at theposition to-be sensed by document detector 45. This is illustrated in FIGS. 4 and 5. It is seen in FIG. 4 that document in stacker 20 has not as yet settled upon the stack of documents. Document tail kicker has been potentiated by document 25 and shutter plate 32 is blocking the light from impinging upon light sensitive element 41. Although, under these conditions there will be an output from light sensitive detector 40, motor 50 of FIG. 3 will not be operated to lower stacker platform 22 because the next document 25 to enter stacker 20 is not in a position to be sensed by document detector 45. Further, it is seen in FIG. 5 that the document in stacker 20 has settled down and that the next document to enter stacker 20 is in position to be sensed by document detector 45. However, the shuttle plate 32 is no longer blocking light from light sensitive element 41. Hence, motor 50 will not be operated to lower stacker platform 22.

The stacker platform 22 as seen in FIG. 3 is fixed to platform support 23 which rides along stabilizing shaft 51. Backplate 55 is provided with vertical slot 56 to accommodate vertical movement of platform support 23. Platform support 23 moves vertically under control of motor 50. The drive shaft 52 of motor 50 drives toothed pulley 53. Toothed pulley 53 in turn drives pulley 57 by means of toothed belt 54.

Pulley 57 is fixed to the end of lead screw 58. An elevating nut 59 is carried by lead screw 58 and moves either up or down depending upon the direction in which motor 50 is driven. Platform support 23 is coupled to the elevating nut by means of plate 60 which has a projecting end 61 merely bearing against upper surface 62. This coupling arrangement is merely a safety arrangement and stacker platform support 23 could be fixed to elevating nut 59. Coupling plate 60 is fixed to platform support 23 so that its projecting end 61 normally rests upon upper surface 62 of elevating nut 59. By this arrangement, platform support 23 follows the movement of elevating nut 59. However, if some obstruction such as an operators hand came in the path of platform support 23 as it is moving downwardly, then platform support 23 would disengage from elevating nut 59 and only the weight of the platform support 23 would bear upon the obstruction. It should be noted that plate 65 is attached to elevating nut 59 and prevents platform support 23 from rotating.

Stacker platform 22 reaches an upper limit as seen in FIG. 3 when elevating nut 59 operates upper limit switch 70. Stacker platform 23 is in a lower limit condition when elevating nut 59 operates lower limit switch 71.

The circuit for controlling the operation of motor 50 is shown in FIG. 9. The signals for controlling motor 50 so as to move the stacker platform 22 up and down come from AND circuits 75 and 76 respectively. When power is supplied, for example, by operating a start key, AND circuit 75 will be conditioned to pass a signal for operating motor 50 so that it rotates lead screw 57 in a direction to advance elevating nut 59 upwardly until elevating nut 59 operates upper limit switch 70. When upper limit switch is operated the Not Upper Limit condition will be down and there will not be a signal from AND circuit to operate motor 50. I

Likewise, there will not be an output from AND circuit 76 to operate motor 50 because the input conditions for AND circuit 77 are not satisfied at this time. It should be noted that AND circuit 76is conditioned to pass a signal from single shot multivibrator 78 because Stacker Full latch 91 was reset when the start key was operated. Also, since the Upper Limit condition exists, OR circuit 88 provides a Stacker In Position signal.

The input conditions to AND circuit 77 are satisfied under the conditions illustrated in FIG. 6. The conditions represented in FIG. 6 are reached when the level of documents accumulated upon platform 22 is such that document tail kicker 30 is held upwardly and shutter plate 32 is activating light sensitive detector 40. Under these conditions, sense amplifier 79 provides a signal to AND circuit 77. Then, when the next document 25 reaches a position where it is sensed by document detector 45 as seen in FIG. 6, sense amplifier 80, FIG. 9, also provides a signal to AND circuit 77. AND circuit 77 is conditioned at this time by a signal from lower limit switch 71 indicating that stacker platform 22 is not in the lower limit position. The signal passed by AND circuit 77 under these conditions fires single shot multivibrator 78. The duration of the signal from single shot multivibrator 78 is such that AND circuit 76 will have an output for operating motor 50 to lower platform 22 approximately one-half inch.

The conditions representing the operation after the stacker platform has been lowered approximately onehalf inch are shown in FIG. ,7. FIG. 5 illustrates the conditions just prior to themotor 50 being operated to lower stacker platform 22. In FIG. 5 it is seen that document detector is activated by a document 25, how ever, document tail kicker 30 has not been moved to a position where shutter plate 32 is operating light sensitive detector 40. Consequently, not all of the input conditions to AND circuit 77 are satisfied and thus, there is not an output from AND circuit 77 to fire a single shot multivibrator 78.

The documents continue to enter stacker 20 and the condition in FIG. 6 is again reached. Motor 50 is again operated to lower stacker platform 22 to the position as shown in FIG. 7. The process repeats until a stacker full condition occurs. When the stacker is full, AND circuit 77 will no longer be conditioned and even though there are simultaneous outputs from amplifiers 79 and 80, AND circuit 77 will not pass a signal to fire single shot multivibrator 78. However, the signals from amplifier 79 and 80 will activate AND circuit 90 which isconditioned by the Lower Limit signal from lower limit switch 71 which ispassed to AND circuit 90 via OR circuit 89.

The signal passed by AND circuit 90 is applied to set stacker full latch 91. The output of stacker full latch 91 is applied to activate indicator light 92 and to stop movement of the document transport which includes belts 10 and 15. The documents are then unloaded from the stacker and the start key is again operated so as to move stacker platform 22 to the upper limit position as previously described. When the stacker platform reaches the upper limits position, OR circuit 88 passes a signal to indicate that the stacker platform 22 is in position and documents may be delivered to the stacker. if, for some reason not all of the documents were removed from the stacker, then after the start key is operated, stacker platform 22 is elevated until the documents operate tail kicker and shutter plate 32 activates light sensitive detector 40. Under these conditions, AND.circuit 87 passes a singal via OR circuit 88.

to indicate that stacker platform 22 is in position.

A jam condition is illustrated in FIG. 8. This conition is detected by sensing for two consecutive signals for lowering the stacker platform 22. The first signal for lowering the stacker platform 22 is generated by single shot multivibrator 78 and applied to trigger 84 via inverter 83. Thus, trigger 84 is set when the signal from single shot multivibrator 78 times out. Normally,

stacker platform 22 is lowered under these conditions and shutter plate 32 is no longer activating light sensitive detector 40. However, when there is a document jam condition, there is a signal from light sensitive detector 40 and the signal from amplifier 78 is inverted by inverter 82 so that trigger 84 is not reset. Then, when the next signal is passed by AND circuit 77 to fire single shot multi vibrator 78, ie, when the next document 25 activates document detector 45, the input conditions to AND circuit 85 are satisfied because trigger 84 is still set. The output signal from AND circuit 85 is passed by AND circuit 86 because the Not Lower Limit signal is available to condition AND circuit 86. Of course, inverters 81 and 82 prevent AND circuit 75 from passing a signal to operate motor 50. The signal passed by AND circuit 86 for indicating a jammed condition is used to stop the document transport. It also energizes indicator light 93 for indicating a documentjam condition.

From the foregoing, it seems that the invention provides improved apparatus for controlling the movement of the stacker platform. It is also seen that the document tail kicker which is operated by documents entering the stacker is used together with a document sensor for indicating that the documents accumulating upon the document platform have reached a level where the stacker platform must be lowered in order that the documents may continue to properly stack. It is seen that stacker platform is lowered repeatedly when the proper conditions are detected until a stacker full condition is reached. It is also seen that logic circuitry has been provided to detect and indicate a stackerjam condition.

What is claimed is: 1. Apparatus for controlling an article stacker comprising an article support for collecting articles delivered thereto inseriatum, said article support having one end positioned at said article delivery position,

article deflecting means located at said article delivery position to be actuated by the leading portion of a delivered article and responsive to being actuated to deflect the trailing portion of said delivered article toward said article support,

article deflecting sensing means for generating an indication upon detecting said article deflecting means in said actuated position, article sensing means for generating an indication in response to an article approaching said delivery position, said article sensing means being positioned relative to said article deflecting sensing means a distance less than the, distance between articles, and

means for generating a control indication in response to simultaneous indications from said article deflecting sensing means and said article sensing means.

2. Apparatus for controlling an article stacker including a bi-directional movable support for collecting articles delivered thereto inseriatum, drive means coupled to said support to move the same bi-directionally and control means for controlling said drive means said control means comprising:

article deflecting means located at said article delivery position to be actuated by the leading portion of a delivered article and responsive to being actuated to deflect the trailing portion of said delivered article toward said article support,

first sensing means for generating a signal upon detecting said article deflecting means in said actuated position,

second sensing means for generating a signal in response to an article approaching said delivery position, said second sensing means being positioned relative to said article deflecting sensing means a distance less than the distance between articles control signal generating means for generating a control signal in response to simultaneous signals from said first and second sensing means, and

means for supplying said control signal to said drive means to cause the same to move said support a pre-determined amount in a pre-determined direction.

3. The apparatus for controlling an article stacker as in claim 2 further comprising limit switch means for generating a signal in response to said movable support reaching a pre-determined position, and

means for generating a signal for indicating a stacker full condition in response to signals from said first and second sensing means, and said limit switch means. 1

4. The apparatus for controlling an article stacker of claim 2 further comprising means for generating a stacker jam condition in response to detecting two successive signals from said control signal generating means simultaneously with a signal from said first sensing means. 7

S. The apparatus for controlling an article stacker as in claim 2 wherein said control signal generating means comprises a logical AND circuit having inputs connected to said first and second sensing means to generate an output signal when signals are simultaneously present from said first and second sensing means, and

single shot multivibrator means connected to be fired by an output signal from said logical AND circuit to provide a control signal having a predetermined time duration.

6. The apparatus for controlling an article stacker as in claim 3 wherein said means for generating a signal for indicating a stacker full condition comprises a logical AND circuit having inputs connected to receive signals from said limit switch means and from said first and second sensing means to provide an output signal when signals are simultaneously present from said first and second sensing means and said limit switch means, and

a bi-stable logical circuit element connected to said AND circuit to be switched to a set state upon receiving an output signal from said logical AND circuit, said bi-s'table logical circuit element providing a stacker full indication when in its set State.

7. The apparatus for controlling an article stacker as in claim 4 wherein said means for generating a stacker jam condition comprises a bistable logical circuit element switchable to a set state in response to a signal from said control signal generating means and switchable to a re-set state in response to the absense of a signal from said control signal generating means, and

a logical AND circuit connected to receive a signal from said bi-stable'logical circuit element when the same is in its set state and to receive a signal from said control signal generating means, said AND circuit providing an output signal when said bi-stable logical circuit element is in its set state and said control 'signal generating means is simultaneously providing a signal to said AND circuit. 

1. Apparatus for controlling an article stacker comprising an article support for collecting articles delivered thereto inseriatum, said article support having one end positioned at said article delivery position, article deflecting means located at said article delivery position to be actuated by the leading portion of a delivered article and responsive to being actuated to deflect the trailing portion of said delivered article toward said article support, article deflecting sensing means for generating an indication upon detecting said article deflecting means in said actuated position, article sensing means for generating an indication in response to an article approaching said delivery position, said article sensing means being positioned relative to said article deflecting sensing means a distance less than the distance between articles, and means for generating a control indication in response to simultaneous indications from said article deflecting sensing means and said article sensing means.
 2. Apparatus for controlling an article stacker including a bi-directional movable support for collecting articles delivered thereto inseriatum, drive means coupled to said support to move the same bi-diRectionally and control means for controlling said drive means said control means comprising: article deflecting means located at said article delivery position to be actuated by the leading portion of a delivered article and responsive to being actuated to deflect the trailing portion of said delivered article toward said article support, first sensing means for generating a signal upon detecting said article deflecting means in said actuated position, second sensing means for generating a signal in response to an article approaching said delivery position, said second sensing means being positioned relative to said article deflecting sensing means a distance less than the distance between articles control signal generating means for generating a control signal in response to simultaneous signals from said first and second sensing means, and means for supplying said control signal to said drive means to cause the same to move said support a pre-determined amount in a pre-determined direction.
 3. The apparatus for controlling an article stacker as in claim 2 further comprising limit switch means for generating a signal in response to said movable support reaching a pre-determined position, and means for generating a signal for indicating a stacker full condition in response to signals from said first and second sensing means, and said limit switch means.
 4. The apparatus for controlling an article stacker of claim 2 further comprising means for generating a stacker jam condition in response to detecting two successive signals from said control signal generating means simultaneously with a signal from said first sensing means.
 5. The apparatus for controlling an article stacker as in claim 2 wherein said control signal generating means comprises a logical AND circuit having inputs connected to said first and second sensing means to generate an output signal when signals are simultaneously present from said first and second sensing means, and single shot multivibrator means connected to be fired by an output signal from said logical AND circuit to provide a control signal having a predetermined time duration.
 6. The apparatus for controlling an article stacker as in claim 3 wherein said means for generating a signal for indicating a stacker full condition comprises a logical AND circuit having inputs connected to receive signals from said limit switch means and from said first and second sensing means to provide an output signal when signals are simultaneously present from said first and second sensing means and said limit switch means, and a bi-stable logical circuit element connected to said AND circuit to be switched to a set state upon receiving an output signal from said logical AND circuit, said bi-stable logical circuit element providing a stacker full indication when in its set state.
 7. The apparatus for controlling an article stacker as in claim 4 wherein said means for generating a stacker jam condition comprises a bistable logical circuit element switchable to a set state in response to a signal from said control signal generating means and switchable to a re-set state in response to the absense of a signal from said control signal generating means, and a logical AND circuit connected to receive a signal from said bi-stable logical circuit element when the same is in its set state and to receive a signal from said control signal generating means, said AND circuit providing an output signal when said bi-stable logical circuit element is in its set state and said control signal generating means is simultaneously providing a signal to said AND circuit. 